Laboratory study on the use of EPS-block geofoam for embankment widening

The use of expanded polystyrene geofoam (geofoam block) has been gaining momentum in roadway expansion projects. They are traditionally placed along the slope face of the existing roadway embankment as a side-hill fill. However, previous studies have shown the detrimental effects of seepage forces on the side-hill fill type of geofoam block configurations. In order to improve the performance of traditional embankment-widening configuration under seepage forces, an alternative geofoam block assembly is proposed. For this purpose, a lysimeter with dimensions of 60 cm high, 20 cm wide, and 200 cm long was constructed in the laboratory. A water reservoir located at the end of the lysimeter provided three different constant pressure heads (25 cm-, 38 cm-, and 50 cm-H₂O pressure) during the tests. An embankment-widening geofoam block assembly was placed along the slope face of marginally stable sandy embankment to investigate the effects of seepage on the stability of geofoam block assembly. The dimensions of the geofoam blocks used to construct the embankment-widening sections were 2.5 cm high, 5 cm wide, and 15 cm long. In addition to the laboratory physical testing, factors of safety against global stability and hydrostatic sliding failures were studied through coupled numerical modelling. Stability modelling comprised fully coupled variably saturated flow and conventional limit equilibrium analysis to quantify the performance of the lysimeter test against global stability failure. Factor of safety against hydrostatic sliding was quantified using fully coupled variably saturated flow and stress-deformation modelling. Both laboratory and numerical models showed that the proposed geofoam block configuration significantly improved the performance of traditional side-hill fill embankment-widening technique under seepage forces.